1. Field of the Invention
The present invention relates to a liquid crystal display, and more particularly, to an in-plane switching mode liquid crystal display and a fabricating method thereof.
2. Discussion of the Related Art
Cathode-ray tubes have generally been used until recently as display devices. Currently, efforts are being made to study and develop various types of flat panel displays, such as liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), and electro-luminescence displays (ELD), as alternatives to CRTs. Particularly, the interest in LCD is high because it is light, thin, compact, consumes less power, and displays high resolution images.
A vertical alignment mode (VA) has generally been used for fabricating an LCD. The VA LCD includes two substrates spaced apart and facing each other, and a liquid crystal material layer interposed between the two substrates. Each of the two substrates includes a plurality of electrodes facing each other. A voltage applied across the electrodes induces an electric field in the liquid crystal material layer. An alignment of liquid crystal molecules within the liquid crystal material layer is changed in accordance with an intensity or direction of the induced electric field, thereby changing light transmissivity through the liquid crystal material layer. Thus, the VA LCD displays images by varying the induced electric field. However, since the VA LCD is driven by the induced electric field between the two substrates, the VA LCD has a narrow viewing-angle. An in-plane switching mode (IPS) LCD has been proposed to increase viewing-angle of the VA LCD.
FIG. 1 is a cross-sectional view of a related art IPS LCD. Referring to FIG. 1, an IPS LCD B includes a color filter substrate B1, an array substrate B2, and a liquid crystal material layer 90 interposed between the color filter substrate B1 and the array substrate B2. A thin film transistor T, a common electrode 58 and a pixel electrode 72 are disposed in respective pixels P1 and P2 defined on a substrate 50 within the array substrate B2. The thin film transistor includes a gate electrode 52, semiconductor pattern 62 on a gate insulating layer 60, and source and drain electrodes 64 and 66 apart from each other. The common electrode 58 and the pixel electrode 72 are apart from and parallel to each other in the same substrate, i.e. the array substrate B2.
A black matrix 32 is disposed over the thin film transistor T on the color filter substrate B1. Respective color filters 34a and 34b are disposed over respective pixels P1 and P2. An alignment of liquid crystal molecules in the liquid crystal material layer 90 is changed by the in-plane electric field induced between the common electrode 58 and the pixel electrode 72.
FIG. 2 is a plan view of an array substrate of an IPS LCD according to the related art. Referring to FIG. 2, a plurality of gate lines 54 and at least one data line 68 are disposed on a substrate 50. Crossings of the gate lines and the at least one data line define a pixel region P. A thin film transistor T is disposed near each crossing of the gate lines 54 and the at least one data line 68. A common line 56 is apart from the gate line 54 and traverses the pixel region P. The thin film transistor T includes a gate electrode 52, a semiconductor pattern 62, and source and drain electrodes 64 and 66. The common electrode 58 and the pixel electrode 72 are apart from and parallel to each other. Liquid crystal molecules of the liquid crystal material layer 90 (shown in FIG. 1) are arranged along a rubbing direction RD of the alignment layer (not shown) in an initial stage.
FIG. 3A is a plan view of an alignment of liquid crystal molecules in the IPS LCD of FIG. 2 when no in-plane electric field is induced. Referring to FIG. 3A, no in-plane electric field is induced between the common electrode 58 and the pixel electrode 72. In this instance, a liquid crystal molecule 90 is arranged along a rubbing direction RD.
FIG. 3B is a plan view of an alignment of liquid crystal molecules in the IPS LCD of FIG. 2 when an in-plane electric field is induced. Referring to FIG. 3B, an in-plane electric field 95 is induced between the common electrode 58 and the pixel electrode 72. In this instance, the liquid crystal molecule 90 is arranged along an specific direction OD between the rubbing direction RD and the induced in-plane electric field 95.
Light transmissivity is highest when an angle between the specific direction OD and the rubbing direction RD is 45 degrees. However, when the in-plane electric field 95 is stronger, the liquid crystal molecule 90 tends to be arranged near the in-plane electric field 95. Therefore, the angle between the specific direction OD and the rubbing direction RD is greater than 45 degrees, thereby significantly reducing light transmissivity.